Refracting container for illuminating means.



c. HEWITT. I REFRACTING CONTMNER FOB:lLLUMINATIMG MEANS APPLICATIONFILED 052.20, 1912.

1 Patented Mar. 2 1 1 UNITED STATESTPATENT oFFIo'E;

PETER coornn HEWITT, or nrucwoon maivon, new JERSEY.

BEFR ACTING CQNTAINEB FOR ILLUMINATING MEANS.

Patented Mar. 28, 1916.

greaterangle than does the light striking the 1 117325 7 7 Specificationof Petters Patent.

I Application filed December 20, 1912. Serial No. 737,867.

- To all whom ifmay concern: I

Be It known that 1, PETER COOPER Hnwrr'r,

7 of light, such, for instance, as electric arcs,

a citizen of the United States, and resident of Ringwood Manor, in thecounty 'of Passaic and State of New Jersey, have invented certain newand useful Improvements in Refracting Containers for Illuminating Means,of which the following is a specification.

This invention has for its object the directingv and diffusing-of lightby refraction and is applicable for use with any common sourceincandescent'filaments or mantles, gas flames or thelike. In my priorapplication, Serial No. 708,421, filed July 9, 1912, I haveillustratedan electric incandescent lamp having cover) that by the outer surface ofthe bulb provided with refractorsin the form of depressions andelevations encircling the bulb and serving to refract a portion ofthelight in the direction of the 'endsof the bulbs which are comparativelydark in the ordinary tungsten lamp with zigzag filaments. I

' My present invention results from my disproviding a series ofrefractors each w itsbase toward a" source of light, I can so formthe'refractors and so position them in respect to the source of lightthat substantially all'of the light entering the base of each refractorwillbe emitted, and, furthermore, will be emitted from a single outersurface of the refractor. This I accomplish by'such, a formation and arerangement of the refractors and such positioning of them in respect tothe source of light that one portion of the light entering .the base ofeach 'refractor will be reflected one or more times within the refractorand emitted from an outer surface, and another portion of the lightenterlng the base will be reflected a greater number of times within therefractor and emittedfrom the same outer face as the first-mentlonedportion.

To this end I arrange the several refractors with respect to each otherand the source of light with respect to all of them, so that the I raysof light will traverse each refractor at an angle to the bisector of theouter angle of the refractor and so thatthe light entering the base andtraversing the glass of each 'refractor will strike one outer surface ata other outer surface, preferably that striking the farther side beingsingly reflected and emitted through the'near'er side, and that directlystriking the nearer side'will do so at a smaller angle and be reflectedto the farther side and thence back and emitted from the nearer side.Thus, substantially all'of the light entering'the base from the source.will'be .emitted in one direction and upon the same side of saidbisectors of said outer angles.

The principle of my invention according to which the scope. andreasonable equivalents thereof may be judged is best illustrated in thesimplest geometrical form in which I have contemplated embodying thesame, for instance, the lower portion ofthe container or the portion inthe direction of which it is desired to direct the illumination may beapproximately a hemisphere, so, that the bases of the prisms may beconsidered as approximate planes, the transverse curvatures of the Zonesof each base being small. The

prisms formed on the outside of such a container will be simplest whentheir crosslike be employed, andthe equatorial diameter or plane will beat right-angles thereto.

In such an arrangement and with isosceles triangles, the source of lightshould be at one side of the normal to the base of each refractor andthe angles to be given'the exterior or light-emissive sides of theprisms ill depend upon the index of refraction of the particular glassused, as, for instance, an ordinary index of refraction glass such asmay be used, may be, say 1.52. In such case the angle of the sidesof-the refractors may be 32 34'. In such case and with any source oflight suitably located in the polar axis and below therequatorial plane,the

light will be, in the case of each and all'r'e- 'fractors, emitted onthe side of the'prism refractor. presented in the direction of the polardiameter, that is, away from the equa-v tor'ial plane. As I have aboveexplained this will be accomplished by.single reflection of some of therays and by double reflection of other rays; the. rays of light enteringthe base of any prisms in such-manner asto seek to emerge from the prismsurface on the side toward the equatorial plane, will be reflected onceby total reflection and will thus strike the opposite face of -the prismat an angle of light emission.

the baseof the prisms and traverses the glass to the outer surface andseeks to emerge from the surface directed away from the equator'i'alplane, will strike it at a muchmore acute angle than the rays firstmentioned:

These rays will be totally reflected, and will again traverse the glassacross the prism to the surface presented toward the equatorial plane.where the angle will be again found to be an angle of total reflection,but these two total reflections will have resulted .in bringing the raysso nearly perpendicular to the surfacesthat upon again traversing theglass and a secondtime approaching the outer surface presented in thedirection away from the equatorial plane, the angle 'will be an angle oflight emission. Thus light entering the bases of the prisms andtraversing the interior thereof will strike both the outer-or emissive'surfaces of the prisms, but will all be emitted from one of them only.As all of these emissive surfaces are presented in one direction alllight falling on the interior of the lower hemisphere will be emitteddownwardly.

With the-angles which I have above described, the above result willfollow any displacement of'the light below the equa orial plane, and asimilar effect will be produced even if the light, be somewhat displacedfrom the exact polar axis of the container. It will "be evident,however, that similarly operat ing prism angles having thecharacteristic single'reflectiojn followed bv emission as to part of thelight, and double reflection followed by emission on the same side as toanother portion of the light, may be achieved by sprisms which are notexactly isosceles and in containers which are not exactly hemispherical.

. I have dBSCIIbQd thB container thus far as hemispherical only, and itis obvious; that the upper portion of the containermay also "far asconcerns the case of the isosceles tri- 5 At the same' time that portionof the light which enters I do not mean necessarily the angle at whichthe outer faces meet, as the. outer edge of the refractor may betruncated or rounded off,

but domean the angle at which the major portions .of the faces lie inrespect to each other. These faces may be very slightly curved eitherconcave or convex, and commerciall'y satisfactory results may still beobtained. I have mentioned the-{angle as being 32 34" and this is.substantially correct'tor glass having an index of refraction of 1.52,but it isevident that. with variations in, the index there must be acorre'sponding. change in the angle for the most eflicient results.Furthermore, this angle is not the only possible'one for a given glassbut-is merely the most efiicient'one- As the "angleof the facesdecreases-'or'increases from this,

the range or space within which thesource .of light must be located,for'eflicient direct-. ing action, decreases. E'flicient results may. beobtainedthrough -a variation of several' degreeseach way from'32 34for'glass of 13.52 index of refraction and in special'cases 90 much of adeparture from the angle 32 34' theremay be quite a wide divergence, but

causes the results to be seriously modified. My mventlon is particularlyuseful in connection with. overhead lights, the refrac tors beingarranged to encircle and extend beneath the source of light. I Thesourceoflight and refractors are so'positioned in respect to each other andthe refractors are so formed that the source of light will be below thebis'ector of the outer angle of each refractor and each-refractor willemit substantially'all of the light received" by it downwardly from itslower face and all of therefractors will emit light in the samehemispherical direction that is to sa' v,-sttbstantially all the lightwill radiate'in one loo hemispherical region lying on one "side of ahorizontal plane passing through the -to'p of the lamp. Furthermore,these-refractors may 'be properly formed and arranged to secure thisresult. and, at the same time. all or substantially all of'the lightemitted from each refractor will clear the outermost portion or tip ofthe. adjacent refractor below it. To secure downward distribution, the

source of light should be below the bisectorv of angle between the outersides of each refractor, so that a larger part of the light will strikethe upper face-of the refra'tor than strikes the lower. It is onlyimportant that the bisectorof the angle pass on the opposite side of thesource of light from that in which it isdesired' todirect the light, so

angle prisms, in' which such bisector 1s always perpendicular to thebase, but in de' signing any modificat onsiwithin the spirit,

of my invention. the angle of the light after it has entered the baseand been refracted and while'it is traversing the lnterior of the In thedrawings: Figure 1 is a diagram- 1 matic representationof a sectionthrough a spherical container with lines representing certain light raysfrom a source of light in two diflerent positions. Fig. 2 is a centrallongitudinal'section through a portion of'a container the source oflight being con en-' tionally represented as an are light. Fig. 3 is aside elevation of the container-shown in Fig. 2.

The diagram forming Fig. 1 of the drawing represents a central verticalsection through a spherical container 10 with a series of refractors 11upon its'outer surface. The center of the container is at the point '12and a source of light is represented in two different positions 13 and14. The refractors are of isosceles form'in cross section, that is thebisector of the angle between the two outer sides of each refractorpasses through the center point 12 and such bisectors are coincidentwith lines normal to the bases of the several refractors at theircenters. The source of light when at the point 13 will have its rays 13and 13 entering the base of each refractor and the lower ray 13 willstrike thelower surface 11 of arefractor and the ray 13" will strike theupper surface 11. As the source of light is below the center of. thesphere the angle of intersection of the ray 13" and surface 11 will bemore acute'than the angle between the upper ray and the upper surface.By forming the. refractors with their outer surfaces at the properanqle, which i angle is substantially 32 and3-H for a glass having aninden of refractatiou of 1.52 the light ray 13 will e totally reflectedby the surface 11,and will pass upwardl toward the upper surface 11*.Here it will be totally reflected a second time and pass downwardlytoward the surface 11% this time striking the latter at such an anglethat it will emerge in a direction upon the same side of the bisector ofthe angle as is the source of light, The light ray 13 willstrike thesurface, 11 at a steeper angle, but will nevertheless be totallyreflected within the refractor 'and pass toward the surface 11. Here itwill emerge in the same general direction as those liqht rayscorresponding to the lightrav 13 and which were doubly reflected. Thusall of the light which enters the base will .be either singly reflectedwithin the refractor or will be doubly reflected and all of saidlightwill emerge on the same'side of the bisector of the angle as is thesource of light. As the refractors encircle the container it will benoted that all of the light rays striking the lower cr-hemisphericalportion will emerge in a general-downward direction" and the light whichstrikes some of the refractors only discussed the light rays from thepoint.

13 which-is only a shortdistance below the center of the sphere but itwill be noted that rays 14* and 1% coming from a lower source 14 will bedirected in the'same manner. It is thus evident that the exact positionof the source is immaterial so long as it is in or substantially in thepolar diameter 0.d and below the plane of the equatorial diameter 6-Experiment will readily show the particular distance below at which thebest results are obtained. but if the source of light be positioned at apoint corresponding to either of the points 13 or 14 or anywhere betweenthe two points, or in their immediate vicinity, satisfactory resultswill be obtained.

In Figs. 2 and 3 I have illustrated a container 15, to a certain extentconventionally and constituting a practical embodiment of my invention,but to avoid confusion I have illustrated the refractors 16 on a muchlarger scale proportionally, than isnecessary in practice. I do not wishto be limited I in any way to any particular sire of refrac tor .or anyparticular number of refractors nor any particular mode or method offorming a series of ridges and grooves by first coating the outersurface of the container with a suitable wax preparati n and marking orcutting grooves through'this coating and along which the glass may beetched away by chemical or embrasi'ye action preferably by hydrofluoricacid. If the refractors of my present invention be formed very minutesubstantially the same method' miqht be employed-for forming them, or ifthey are to be made larger they may be formed by mechanical grinding .orcutting away the glass to leave the refractors'. of the particular shapeor the glass container may be molded with the refractors thereon,

.In Fig.2 the source of light is conventionally illustrated as an arcli'ght- 17,.but as I have previouslypointed out, any well known source flight may be employed. I have also illustrated the upper portion 18 offthe container of substantially cylindrical form with symmetricalrefractors thereon. For a short cylinder length it isevident. that therefractors thereon will all act to'direct the light downwardly. g Y

' It 'will be evident that while I have shown and, described and haveeven specified in certain of the claims. that the bisectors of the ridgeangles of the refractors through the center of curvature of the '40fractors in the form of approximately paralnumber of degrees of theangle of convergence 'of the outer surface of the prisms.Similar'ly,,also, it will be understood that while I refer tothe sourceof light or the center ,of luminosity as being, below the region ofconvergence of the bisect-ors of the ridge angles, the word below doesnot necessarily have any particular significance with respect to thedirection of pull of gravity but is merely used as a convenience formaking clear the novel relative position and relation of the light withreference to g the refractors.

Having thus described my. invention, what I claim as new and desire tosecure by Letters Patent is 1. A transparent wall having refractors inthe form of approximately parallel prismatic ridges 0n the outersurface, each ridge being of triangular cross section throughout I itsextent and each having the straight line elements forming its two outersurfaces 1 converging toward the summit of the ridge at an angle of suchacuteness as to internally reflect all rays falling upon said surfacesthrough the base of the refractor, and to emit the same after at leastone and not more than two such reflections, in combination with meansfor radiating light upon the rear of said transparent wall from pointseccentric to the region of convergence of the bisectors of the ridgeangles of said ,converging surfaces.

2. IILCOIDblIlZltlOIl, a source of light and an enclrcling transparentwallhaving relel prismatic ridges on its outer surface, each ridge beingof substantially the same cross section throughout its extent and eachhaw ing its two outer surfaces converging toward the summit of the ridgeat an angle of such acuteness as to internally reflect all rays fallingupon said gsurfaces through the base of the refractor, and to emit thesame after one or more such reflections, said source of light beinglocated on the other side of said wall, below the region of convergenceof the bisectors of the ridge angle of said converging outer surfaces,whereby substantially all of the emitted light is deflected in the samedirection.

3. A spherically curved transparent wall having refractors in the formof approximately prismatic ridges on its outer surface, each'jridgebeing of substantially the same cross section through its extentandleach having its two outer surfaces converging toward the summit ofthe ridge at an angle of such acuteness as to internally vreflect allrays falling upon said surfaces through the base of-the refractor, andto emit said rays after one or more such internal reflections, each ofsaid ribs having its said outer surfaces disposed so that 'all-bisectorsof the ridge summit of the ridge at an angle which is substantially theequivalent of an angle of thirty-two degrees and thirty-four minutes forglass having an index of refraction at one and fifty-two hundredths,thereby internally reflectingall rays falling upon said surfaces throughthe base of the re-fractor and emitting the same after one or more suchreflections; a

5. A transparent wall having prismatic refractors in the form ofapproximately parallel ridges, each ridge being of substantially thesame cross section throughout its extent and each having its two outersurfaces converging toward the summit of the ridge at an angle which issubstantially the equiyalent of an angle of thirty-two degrees andthirty-four minutes for glass havingan index of refraction at one andfifty-two hundredths, thereby'internally reflecting all rays fallingupon said surfaces through thebase of the refractor and emitting thesame afti one or more such reflections, in combination with a source oflight located below the region of convergence of the bisectors of theridge angle of said converging outer surfaces whereby substantially allof the emitted light is deflected in the same direction. 6. Incombination, a source of light and an encircling spherically curvedtransparent wall having prismatic refractors in the form ofapproximately parallel ridges, each ridge being of substantiallythe-same cross section throughout its extent and each having its twoouter surfaces converging toward the summit of the ridge at an anglewhich is substantially the equivalentof an angle of surfaces through thebase of the refractor,

and emitting said rays after one or more such internal reflections, eachof said ribs having its said outer surfaces disposed so that.allbisectors of the ridge angles of all of the ridg'es Pass through thecenter of curvature of said spherical wall, said source of light beinglocated in the common axis of all saidridges andbelow said center ofspherical curvature, 'whereby Substantially all the light emitted fromsaid wall is deflected downwurdly.

Signed at New Yorli city, in the county .of New Yerk and State of NewYork, this 14thd'ay of December, A. D. 1912. PETER COOPER HEWITT.

' Witnesses: I

CLAIR W. FAIRBANK FLORENCE LEVIEN.

